Validity of the Model of Incompressible Fluid in the Study of Hydraulic Stability of Surge Tanks.

Editorial: Proceedings of the Intenational IAHR Second Symposium on Fluid Motion Stability in Hydraulic Systems with Automatic Control,Bucharest,Romania,October 1-3, 1984.

Rezumat:

The study of stability of surge hydraulic systems provided with surge tanks automatcally governed for constant power output of the turbines,starting with D.Toma and considerd further by L.Escande and Ch.Jaeger has been performerd by using the model of incompressible fluid.In this paper it is shown that Thoma’s least area of cross-section of a surge tank gives a condition for stable behaviour at small oscilations even if we use the model of compressible flow,furnishing in this way a new argument for the validty in this problem of the model of incompressible fluid.The mathematical treatment is based on evidentiating in the equations of propagation (the waterhammer equation) of a small parameter suggesting that space dependece of the discharge in the tunnel may be neglected.An analogous approach,for a diferent problem has been adopted by C.Thirriot.